short comments to performance measures sandbox script

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/uwgarp@86 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
fcstGarch11 handled

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/uwgarp@87 edb9625f-4e0d-4859-8d74-9fd3b1da38cb